Metal salt solutions and surface-coating compositions containing same

ABSTRACT

Surface-coating compositions that comprise an oxidizable organic film-forming resinous vehicle contain from 2 to 5 percent, based on vehicle solids, of a loss-of-dry inhibitor which is a metal salt solution that contains 0.05 to 1.5 percent by weight of cobalt, 0.5 to 3.5 percent by weight of calcium, and 0.5 to 5.0 percent by weight of zinc or zirconium. The metals are present in the loss-of-dry inhibitor as salts of branched-chain aliphatic monocarboxylic acids having 6 to 14 carbon atoms, cycloaliphatic monocarboxylic acids having 6 to 10 carbon atoms, or mixtures of these acids.

United States Patent Gottesman et a1.

METAL SALT SOLUTIONS AND SURFACE-COATING COMPOSITIONS CONTAINING SAMEInventors: Roy T. Gottesman, Glen Rock;

George M. Kagan, Edison; Joseph Fath, Princeton, all of NJ.

Tenneco Chemicals, Inc., Saddle Brook, NJ.

Filed: Jan. 21, 1974 Appl. No.: 435,075

Assignee:

US. Cl 260/22 R; 260/24; 260/25; 260/336 R; 106/264; 106/265 Int. Cl.C08L 91/00 Field of Search 260/22 R, 33.6; 106/264, 106/265, 310

References Cited UNITED STATES PATENTS OTHER PUBLICATIONS Payne, OrganicCoating Technology, Vol. I, John Wiley & Sons, Inc., 1954, pp. 232-237.

Singer, Fundamentals of Paint, Varnish, and Lacquer Technology, TheAmerican Paint Journal Co., 1957, pp. 47-51.

Primary ExaminerLewis T. Jacobs Attorney, Agent, or Firm-Evelyn Berlow 57 ABSTRACT Surface-coating compositions that comprise an oxidizableorganic film-forming resinous vehicle contain from 2 to 5 percent, basedon vehicle solids, of a lossof-dry inhibitor which is a metal saltsolution that contains 0.05 to 1.5 percent by weight of cobalt, 0.5 to3.5 percent by weight of calcium, and 0.5 to 5.0 percent by weight ofzinc or zirconium. The metals are present in the l0ss-of-dry inhibitoras salts of branched-chain aliphatic monocarboxylic acids having 6 to 14carbon atoms, cycloaliphatic monocarboxylic acids having 6 to 10 carbonatoms, or mixtures of these acids.

18 Claims, No Drawings NIETAL SALT SOLUTIONS AND SURFACE-COATTNGCOMPOSITIONS CONTAINING SAME This invention relates to metal saltsolutions that are useful as loss-of-dry inhibitors in protective anddecorative surface-coating compositions that contain an oxidizableorganic vehicle. It further relates to surfacecoating compositions thatcontain these loss-of-dry inhibitors.

Metal salts of organic acids have long been used in surface-coatingcompositions that contain drying oils and other oxidizable vehicles toaccelerate the drying process and to promote the polymerization of theunsaturated oils to dry, mechanically resistant coatings. The metal saltdriers perform efficiently when they are first incorporated into anoxidizable coating, but the coatings frequently exhibit a loss of dryingrate on aging. This loss of drying rate probably results from theadsorption of the metal salts on the surfaces of the pig ments andextenders in the coating or from the inactivation of the driers by thereaction of the soluble metal salts with acidic components of thecoating system to form insoluble metal compounds, which do not functionas driers.

The loss of drying rate that coating compositions undergo on storage canbe inhibited or prevented by incorporating a loss-of-dry inhibitor inthe coating. A number of loss-of-dry inhibitors have been proposed foruse in oxidizable surface-coating compositions, but none has proven tobe entirely satisfactory. For example, basic lead naphthenate has beenwidely used to prevent changes in the drying rate of surface-coatingcompositions on aging. The use of this loss-of-dry inhibitor hasrecently been restricted by legislation that drastically limits theamount of lead compounds that can be present in surface-coatingcompositions. Basic cobalt naphthenate is also an effective Ioss-of-dryinhibitor for oxidizable coating systems. Because it causes unacceptablestaining in white and pastel coatings, this inhibitor can only be usedin dark-colored coatings. Moreover, basic cobalt naphthenate oftencauses extensive wrinkling in paint films when it is used in the amountsthat are necessary to give commercially acceptable drying times.

It has now been found that the loss of drying rate on aging ofsurface-coating compositions that contain oxidizable organic vehiclescan be minimized or prevented by incorporating in the compositionscertain solutions of metal salts. These solutions, which contain cobalt,calcium, and either zinc or zirconium salts, are at least as effectiveas the previously known loss-of-dry inhibitors. They do not, however,containtoxic metal salts, and they do not cause staining of white andpastel coatings at the levels at which they are used to inhibit loss ofdry. Unlike the previously known loss-of-dry inhibitors which are pastesthat must be ground into the coating compositions, the metal saltsolutions of this invention are stable, free-flowing liquids that can beadded to the coating compositions at any stage of their manufacture. Inaddition to serving as loss-of-dry inhibitor in surface-coatingcompositions that contain conventional metal salt driers, the metal saltsolutions of this invention can be used as a combinationdrier-loss-ofdry inhibitor in compositions that do not contain metalsalt driers.

The loss-of-dry inhibitors of this invention are solutions ofoil-soluble metal salts that contain 0.05 to 1.5 percent by weight ofcobalt, 0.5 to 3.5 percent by weight of calcium, and 0.5 to 5.0 percentby weight of either zinc or zirconium. The solutions that have the bestcombination of loss-of-dry inhibition, stability, and solubilitycharacteristics contain 0.5 to 1.2 percent by weight of cobalt, L0 to2.5 percent by weight of calcium, and 2.5 to 4.0 percent by weight ofzinc or zirconium. The solutions that contain cobalt, calcium, and zincsalts are generally more effective as loss-of-dry inhibitors than thosethat contain cobalt, calcium, and zirconium salts.

The novel loss-of-dry inhibitors are solutions of oilsoluble metal saltsof branched-chain aliphatic monocarboxylic acids having 6 to 14 carbonatoms, cycloaliphatic monocarboxylic acids having 6 to 10 carbon atoms,or mixtures of these acids. Illustrative of these acids areZ-ethylbutanoic acid, 2,2-dimethylpentanoic acid, Z-ethylpentanoic acid,2-ethyl-4-methylpentanoic acid, 2-ethylhexanoic acid, isooctanoic acid,isononanoic acid, isodecanoic acid, 2-ethyldecanoic acid, isotridecanoicacid, isotetradecanoic acid, cyclopentanoic acid, methylcyclopentanoicacid, cyclohexanoic acid, methylcyclohexanoic acid,1,2-dimethylcyclohexanoic acid, cycloheptanoic acid, and the like. Thepreferred acids for use in the preparation of the metal salts are thebranched-chain aliphatic monocarboxylic acids having 8 to 10 carbonatoms, such as 2-ethylhexanoic acid, isooctanoic acid,2,2-diethylhexanoic acid, 2- methyl-Z-ethylheptanoic acid,2,2-dimethyloctanoic acid, Z-propylheptanoic acid,3,5,5-trimethylhexanoic acid, 3-ethyloctanoic acid, isononanoic acid,and isodecanoic acid; naphthenic acids, such as cyclopentanoic acid,cyclohexanoic acid, cycloheptanoic acid, and methylcyclohexanoic acid;and mixtures of two or more of these acids. Among the most stable of themetal salt solutions are those that contain cobalt as cobaltZ-ethylhexoate and/or cobalt isononanoate, calcium as calciumnaphthenate, and zinc as zinc 2-ethylhexoate.

The metal salts are added to surface-coating compositions as solutionsof the salts in an inert non-polar organic solvent. The solvent ispreferably a hydrocarbon or a halogenated hydrocarbon. The preferredsolvents include aliphatic and cycloaliphatic hydrocarbons such ashexane, heptane, octane, isooctane, cyclohexane, and cycloheptane;petroleum distillates such as mineral spirits, gasoline, diesel fuel,and fuel oils; aromatic hydrocarbons such as benzene, toluene, xylene,and ethylbenzene; and chlorinated compounds such as chlorobenzenes,carbon tetrachloride, and ethylene dichloride. Particularly preferred asthe solvent in the loss-ofdry inhibitors is mineral spirits that is notphotochemically reactive as defined in Section (R) of Rule 66 of theCounty of Los Angeles Air Pollution Control District and that has adistillation range of about to 200C.

The metal salt solutions may contain an additive that decreases theirviscosities. Such additives include the alkyl acid phosphates describedin US. Pat. No. 2,456,824 and the polyoxyalkylene glycols described inUS. Pat. No. 2,807,553.

The metal salt solutions may be prepared by any suitable and convenientprocedure. They may be prepared by a fusion process in which the oxidesor hydroxides of the metals are reacted with the organic acids in anorganic solvent, or they may be prepared by a precipita- 3 on process inwhich the sodium salts of the acids are :acted in aqueous solution withwater-soluble salts of ie metals, and the precipitated metal salts aresepaited from the aqueous solution and then dissolved in 1e organicsolvent. It is generally preferred that the soltlOl'lS be prepared bydissolving the appropriate nounts of the metal salts in the organicsolvent. The metal salt solutions of this invention can be used 1inhibit the loss of drying rate of a wide variety of sur- .ce-coatingcompositions including paints, varnishes, iamels, printing inks, and thelike that contain an oxilzable organic film-forming resinous vehicle.The velcle may be a drying oil or semi-drying oil, such as lin- :ed oil,soybean oil, tung oil, or dehydrated castor oil, ther in the raw, blown,or heat-bodied form. Altemavely, the vehicle may be an alkyd resin,which is the roduct of the reaction of a polyhydric alcohol such asentaerythritol or glycerol with a dicarboxylic acid lCl'l as phthalicanhydride or isophthalic acid and a |onocarboxylic acid such as soybeanoil fatty acids or nseed oil fatty acids, or an oleoresinous varnish,which the product of the reaction of one of the aforemenoned drying oilsor semi-drying oils with rosin, a modied rosin, or a phenolic resin.

The surface-coating compositions to which the lossf-dry inhibitors areadded preferably contain convenonal metal salt driers. Among the mostwidely used of iese driers are the lead, cobalt, manganese, calcium, ridzinc salts of naphthenic acids, octanoic acids, nonrioic acids, and talloil acids. The metal salt solutions an also be used as combinationdrier-loss-of-dry inhibor in compositions that do not contain metal saltdri- In addition to the oxidizable organic film-forming :sinous vehicle,loss-of-dry inhibitor, and metal salt riers, the surface-coatingcompositions of this invenon may contain pigments, extenders, solvents,plastiizers, antiskinning agents, and other additives in the mountsordinarily used in such compositions. Illustrave of the pigments thatare used in surface-coating Jmpositions are titanium dioxide, ferricoxide, calium oxide, zinc oxide, antimony trioxide, kaolin, china lay,calcium carbonate, silica, talc, zinc chromate, arbon black, andmixtures thereof. The useful solvents iclude benzene, toluene, xylene,naphtha, mineral airits, hexane, isooctane, and petroleum ether as wellwater for water-based surface-coating compositions. The invention isfurther illustrated by the following xamples.

EXAMPLE 1 A metal salt solution was prepared by mixing toether thefollowing materials:

The resulting solution was a free-flowing liquid. 1t lowed excellentstability when stored at 25C., 5C., or 49C. for 5 months.

EXAMPLE 2 A metal salt solution was prepared by mixing together thefollowing materials:

Parts by Weight Metal Cobalt Z-ethylhexoate (12% Co) 45.88 0.551 Cobaltisononanoate 12% Co) 4.12 0.049 Calcium Z-ethylbexoate (6% Ca) 483.001.932 Calcium isononanoate (6% Ca) 42.00 0.168 Zinc 2-ethylhexoate (16%Zn) 163.76 2.948 Zinc 'sononanoate (16% Zn) 14.24 0.256 Mineral spirits(Distillation range 157C.l92C.) 232.00 Tripropylene flyeol 15.00

The resulting solution was a free-flowing liquid. It contained a verysmall amount of precipitate after it had been stored at 25C. or 49C. for1 week.

EXAMPLE 3 A metal salt solution was prepared by mixing together thefollowing materials:

This solution, which was a free-flowing liquid, showed slightprecipitation after it had been stored at 25C. or 49C. for 1 week.

EXAMPLE 4 A metal salt solution was prepared by mixing together thefollowing materials:

Parts by Weight Metal Cobalt 2-ethylhexoate 12% Co) 12 ZincZ-ethylhexoate (16% Zn) 178 32 Calcium Z-ethylhexoate (6% Ca) 525 2.1Mineral spirits (Distillation range l57C.-192C.) 232 Tripropylene glycol15 The resulting solution was a stable, free-flowing liquid.

EXAMPLE 5 A metal salt solution was prepared by mixing together thefollowing materials:

Parts by k Weiflit Metal Cobalt Z-ethylhexoate (12% Co) 100 1.2Zirconium Z-ethylhexoate 18% Zr) 178 3.2 Calcium 2-ethylhexoate (6% Ca)525 2.1 Mineral spirits (Distillation range l57C.-l92C.) 232Tripropylene glycol 15 The resulting solution was a stable, free-flowingliquid.

EXAMPLE 6 a. A white enamel was prepared by grinding together thefollowing materials on a pebble mill:

Parts by Weight Titanium dioxide (rutile) 75.0 Zinc oxide 7.5 Long oilsoybean oil phthalic 120.0

anhydn'de alkyd resin (Aroplaz l24l-70) Mineral spirits 24.0

b. To portions of the white enamel was added either (i) 5 percent, basedon the weight of vehicle solids, of the metal salt solution of Example1, (ii) a control drier system containing 0.06 percent, based on theweight of vehicle solids, of cobalt as cobalt Z-ethylhexoate and cobaltisononanoate and 0.12 percent, based on the weight of vehicle solids, ofzirconium as zirconium 2 ethylhexoate and zirconium isononanoate, or(iii) 0.3 percent, based on the weight of vehicle solids, of acommercially-available loss-of-dry inhibitor that contains basic cobaltnaphthenate (Cobalt 254) plus the aforementioned control drier systemcontaining cobalt and zirconium salts.

The metal salt solution of Example 1 and the control drier system wereadded to the enamel at the let-down stage. The basic cobalt naphthenatewas ground into the enamel.

c. Films of the resulting enamels were dried overnight. The yellownessindex and the reflectance of each of the films were measured on 1.5 milfilms with a Hunter Model D-25 Color and Color Difi'erence Meter afterthe films had dried overnight and after they had aged for 3 weeks at25C. The results obtained are summarized in Table I.

Higher readings indicate greater yellowness "Lower readings indicatemore grayness The data in Table I demonstrate that the enamel containingthe metal salt solution of Example l showed a color response comparableto that of the control enamel that contained the cobalt and zirconiumsalts and that both of these enamels were significantly less discoloredthan that containing basic cobalt naphthenate.

EXAMPLE 7 To portions of the white enamel whose preparation is decribedin Example 6a was added 0. l 6 percent by weight of an antiskinningagent (Exkin 2) and either (i) the metal salt solution of Example 4,(ii) the metal salt solution of Example 5, (iii) a drier system thatprovided 0.048 percent of cobalt as cobalt naphthenate and 0.48 percentof lead as lead naphthenate, based on the weight of vehicle solids, or(iv) a commercially available loss-of-dry inhibitor containing basiccobalt naphthenate plus the aforementioned drier system containingcobalt and lead salts. The amounts of the metal salts added are shown inTable ll.

The drying times of films of the freshly-prepared and aged enamels weremeasured on 2 mil wet films at 25C. and 50 percent relative humidityusing Improved Gardner Circular Dry Time Recorders. The results obtainedare given in Table ll.

EXAMPLE 8 a. A red enamel that is prone to loss-of-drying rate on agingwas prepared by grinding the following materials together on a pebblemill:

Parts by Weight Toluidine red pigment 18.75 (Imperial X2741) Long oilsoybean oil phthalic l09.75 anhydn'de alkyd resin (Aroplaz l24l-70)Mineral spirits 62.50 Antiskinning agent (Exkin 2) 0.25

Table [I Enamel Enamel Enamel Containing Containing Containing EnamelMetal Salt Metal Salt Basic Containing Solution Solution Cobalt NoLoss-ofof Ex. 4 of Ex 5 Naphthenate Dry Inhibitor boss-of Dry Inhibitor(based on vehicle solids) 4% 5% 4% 5% 0.25% None Drying Time(HourszMinutes) Initial Set-to-touch :40 0:40 0:40 0:40 0:35 0:35Dusbfree 1:40 1:55 1:40 1:40 1:50 2:15 Thru dry 3:35 3:30 3:40 3:30 3:203:45 After g at 49C.

for 2 onths Set-to-touch l :05 l :00 0:40 0:40 0:40 Dust-free 2:45 22:30 2:20 2:15 2:30 Thru dry 7:15 6:30 6:10 10:00 l0:00

The drying times of films of the freshly prepared and aged enamels weremeasured by the procedure described in Example 7. The results obtainedare given in The data in Table III show that the enamel containing themetal salt solution of Example 3 showed little lossof-dry on acceleratedaging, whereas the enamel containing the conventional drier systemshowed considerable loss-of-dry.

EXAMPLE 9 a. A black enamel that is prone to loss-of-dry on This enamelcontained 39.75 percent vehicle solids.

To this enamel was added an amount of a conventional drier system thatprovided 0.05 percent cobalt, 0.20 percent zirconium, and 0.03 percentcalcium, the percentages being the percentage of metal based on theweight of vehicle solids.

b. To portions of the black enamel of Example 9a was added either (i) 3percent, based on the weight of vehicle solids, of the metal saltsolution of Example 1 or (ii) 2.5 percent, based on the weight ofvehicle solids, of a commercially available loss-of-dry inhibitor thatcontains basic lead naphthenate and that is marketed as Nuact.

c. The drying times of films of the freshly prepared and aged enamels ofExample 9b and of the enamel of Example 9a were determined by theprocedure described in Example 7. The results obtained are given inTable IV.

The results in Table IV demonstrate that the metal salt solution ofExample 1 was more effective than the lead-based comparator as aloss-of-dry inhibitor in the black enamel.

Table IV Enamel Containing Enamel Containing Enamel Containing Driersand Driers and Driers, but no Metal Salt Basic Lead Lmof-Dry Solution ofEx. 1 Naph'dienate Inhibitor Drying Time (HourszMinutes) lniSet-to-touch l :25 l :2 Dust-free 1:30 I l5 1:20 Thru dry 3:10 3;4 Afteraging at 49C.

for 2 Months Set-to-touch l :00 l :00 l :25 Dust-free 2:20 2:20 7: l 5Thru dry 3:50 4:25 10:30

a in with conventional driers was re ared b rindg g p P y g EXAMPLE 10ing together in a ball mill the following materials:

Parts by Weight a. To the red enamel whose preparation is described inExample 8a was added an amount of a drier system that provided 0.052percent of cobalt, 0.29 percent of zirconium, and 0.018 percent ofcalcium. the percentages being the percent of metal based on vehiclesolids. b. To portions of this enamel was added either (i) 2 percent,based on the weight of vehicle solids, of the 9 metal salt solution ofExample 2 or (ii) 2.5 percent, based on the weight of vehicle solids, ofa commercially available loss-of-dry inhibitor containing basic leadnaphthenate (Nuact).

c. The drying times of films of the freshly prepared and aged enamels ofExample 10a and the enamel of Example 8a were determined by theprocedure described in Example 7. The results obtained are given inTable V.

The data in Table V show that the metal salt solution of Example 2 wasequivalent to the lead-based comparator as a loss-of-dry inhibitor inthe red enamel.

salts of acids selected from the group consisting of branched-chainaliphatic monocarboxylic acids having 6 to 14 carbon atoms,cycloaliphatic monocarboxylic acids having 6 to 10 carbon atoms, andmixtures thereof.

7. A surface-coating composition according to claim 6 wherein theoxidizable vehicle is an alkyd resin.

8. A surface-coating composition according to claim 6 wherein theloss-of-dry inhibitor comprises a mixture of said metal salts in aninert non-polar organic solvent.

9. A surface-coating composition according to claim 8 wherein the inertnon-polar organic solvent is a hy- What is claimed is:

l. A surface-coating composition having improved resistance to loss ofdrying rate on aging that comprises an oxidizable, organic, film-formingresinous vehicle and from 2 to 5 percent, based on the weight of thevehicle, of a loss-of-dry inhibitor, said loss-of-dry inhibitor being ametal salt solution that contains 0.05 to 1.5 percent by weight ofcobalt, 0.5 to 3.5 percent by weight of calcium, and 0.5 to 5.0 percentby weight of zinc or zirconium, the cobalt, calcium, zinc, and zirconiumbeing present as salts of acids selected from the group consisting ofbranched-chain aliphatic monocarboxylic acids having 6 to 14 carbonatoms, cycloaliphatic monocarboxylic acids having 6 to carbon atoms, andmixtures thereof.

2. A surface-coating composition according to claim 1 wherein the metalsalt solution contains 0.5 to 1.2 percent by weight of cobalt, 1.0 to2.5 percent by weight of calcium, and 2.5 to 4.0 percent by weight ofzinc or zirconium.

3. A surface-coating composition according to claim 1 wherein thecobalt, calcium, zinc, and zirconium are present in the solution assalts of acids selected from the group consisting of branched-chainaliphatic monocarboxylic acids having 8 to 10 carbon atoms, naphthenicacid, and mixtures thereof.

4. A surface-coating composition according to claim 1 wherein theoxidizable vehicle is an alkyd resin.

5. A surface-coating composition according to claim 1 that additionallycontains metal salt driers.

6. A surface-coating composition having improved resistance to loss ofdrying rate on aging that comprises an oxidizable, organic, film-formingresinous vehicle, metal salt driers, at least one pigment, and from 2 to5 percent, based on the weight of the vehicle, of a loss-ofdryinhibitor, said loss-of-dry inhibitor being a metal salt solution thatcontains 0.05 to 1.5 percent by weight of cobalt, 0.5 to 3.5 percent byweight of calcium, and 0.5 to 5.0 percent by weight of zinc orzirconium, the cobalt, calcium, zinc, and zirconium being present asdrocarbon solvent.

10. A surface-coating composition according to claim 8 wherein the inertnon-polar organic solvent is mineral spirits.

11. A surface-coating composition according to claim 6 wherein theloss-of-dry inhibitor comprises metal salts of acids selected from thegroup consisting of branched-chain aliphatic monocarboxylic acids having8 to 10 carbon atoms, naphthenic acid, and mixtures thereof.

12. A surface-coating composition according to claim 6 wherein theloss-of-dry inhibitor comprises a solution in a hydrocarbon solvent of amixture of metal salts, said solution containing 0.5 to 1.2 percent byweight of cobalt as cobalt 2-ethylhexoate and cobalt isononanoate, 1.0to 2.5 percent by weight of calcium as calcium naphthenate, and 2.5 to4.0 percent by weight of zinc as zinc 2-ethylhexoate.

13. in a surface-coating composition that undergoes loss of drying rateon aging and that comprises an oxidizable, organic, film-formingresinous vehicle, metal salt driers, and at least one pigment, theimprovement that inhibits loss of drying rate on aging and that consistsof incorporating in the surface-coating composition from 2 to 5 percent,based on the weight of the vehicle of a loss-of-dry inhibitor, saidloss-of-dry inhibitor being a solution of metal salts in an inertnon-polar organic solvent and containing 0.05 to 1.5 percent by weightof cobalt, 0.5 to 3.5 percent by weight of calcium, and 0.5 to 5.0percent by weight of zinc or zirconium, said cobalt, calcium, zinc, andzirconium being present as salts of acids selected from the groupconsisting of branched-chain aliphatic monocarboxylic acids having 6 to14 carbon atoms, cycloaliphatic monocarboxylic acids having 6 to 10carbon atoms, and mixtures thereof.

14. The method of claim 13 wherein the loss-of-dry inhibitor contains0.5 to 1.2 percent by weight of cobalt, 1.0 to 2.5 percent by weight ofcalcium, and 2.5 to 4.0 percent by weight of zinc or zirconium.

12 thenate, and 2.5 to 4.0 percent by weight of zinc as zincZ-ethylhexoate.

17. The method of claim 13 wherein the loss-of-dry inhibitor comprises asolution of metal salts in a hydrocarbon solvent.

18. The method of claim 13 wherein the loss-of-dry inhibitor comprises asolution of metal salts in mineral spirits.

1. A SURFACE-COATING COMPOSITION HAVING IMPROVED RESISTANCE TO LOSS OFDRYING RATE ON AGING THAT COMPRISES AN OXIDIZABLE, ORGANIC, FILM-FORMINGRESINOUS VEHICLE AND FROM 2 TO 5 PERCENT, BASED ON THE WEIGHT OF THEVEHICLE, OF A LOSS-OF-DRY INHIBITOR, SAID LOSS-OF-DRY INHIBITOR BEING AMETAL SALT SOLUTION THAT CONTAINS 0.05 TO 1.5 PERCENT BY WEIGHT OFCOBALT, 0.5 TO 3.5 PERCENT BY WEIGHT OF CALCIUM, AND 0.5 TO 5.0 PERCENTBY WEIGHT OF ZINC OR ZIRCONIUM, THE COBALT, CALCIUM, ZINC, AND ZIRCONIUMBEING PRESENT AS SALTS OF ACIDS SELECTED FROM THE GROUP CONSISTING OFBRANCHED-CHAIN ALIPHATIC MONOCARBOXYLIC ACIDS HAVING 6 TO 14 CARBONATOMS, CYCLOALIPHATIC MONOCARBOXYLIC ACIDS HAVING 6 TO 10 CARBON ATOMS,AND MIXTURES THEREOF.
 2. A surface-coating composition according toclaim 1 wherein the metal salt solution contains 0.5 to 1.2 percent byweight of cobalt, 1.0 to 2.5 percent by weight of calcium, and 2.5 to4.0 percent by weight of zinc or zirconium.
 3. A surface-coatingcomposition according to claim 1 wherein the cobalt, calcium, zinc, andzirconium are present in the solution as salts of acids selected fromthe group consisting of branched-chain aliphatic monocarboxylic acidshaving 8 to 10 carbon atoms, naphthenic acid, and mixtures thereof.
 4. Asurface-coating composition according to claim 1 wherein the oxidizablevehicle is an alkyd resin.
 5. A surface-coating composition according toclaim 1 that additionally contains metal salt driers.
 6. Asurface-coating composition having improved resistance to loss of dryingrate on aging that comprises an oxidizable, organic, film-formingresinous vehicle, metal salt driers, at least one pigment, and from 2 to5 percent, based on the weight of the vehicle, of a loss-of-dryinhibitor, said loss-of-dry inhibitor being a metal salt solution thatcontains 0.05 to 1.5 percent by weight of cobalt, 0.5 to 3.5 percent byweight of calcium, and 0.5 to 5.0 percent by weight of zinc orzirconium, the cobalt, calcium, zinc, and zirconium being present assalts of acids selected from the group consisting of branched-chainaliphatic monocarboxylic acids having 6 to 14 carbon atoms,cycloaliphatic monocarboxylic acids having 6 to 10 carbon atoms, andmixtures thereof.
 7. A surface-coating composition according to claim 6wherein the oxidizable vehicle is an alkyd resin.
 8. A surface-coatingcomposition according to claim 6 wherein the loss-of-dry inhibitorcomprises a mixture of said metal salts in an inert non-polar organicsolvent.
 9. A surface-coating composition according to claim 8 whereinthe inert non-polar organic solvent is a hydrocarbon solvent.
 10. Asurface-coating composition according to claim 8 wherein the inertnon-polar organic solvent is mineral spirits.
 11. A surface-coatingcomposition according to claim 6 wherein the Loss-of-dry inhibitorcomprises metal salts of acids selected from the group consisting ofbranched-chain aliphatic monocarboxylic acids having 8 to 10 carbonatoms, naphthenic acid, and mixtures thereof.
 12. A surface-coatingcomposition according to claim 6 wherein the loss-of-dry inhibitorcomprises a solution in a hydrocarbon solvent of a mixture of metalsalts, said solution containing 0.5 to 1.2 percent by weight of cobaltas cobalt 2-ethylhexoate and cobalt isononanoate, 1.0 to 2.5 percent byweight of calcium as calcium naphthenate, and 2.5 to 4.0 percent byweight of zinc as zinc 2-ethylhexoate.
 13. In a surface-coatingcomposition that undergoes loss of drying rate on aging and thatcomprises an oxidizable, organic, film-forming resinous vehicle, metalsalt driers, and at least one pigment, the improvement that inhibitsloss of drying rate on aging and that consists of incorporating in thesurface-coating composition from 2 to 5 percent, based on the weight ofthe vehicle of a loss-of-dry inhibitor, said loss-of-dry inhibitor beinga solution of metal salts in an inert non-polar organic solvent andcontaining 0.05 to 1.5 percent by weight of cobalt, 0.5 to 3.5 percentby weight of calcium, and 0.5 to 5.0 percent by weight of zinc orzirconium, said cobalt, calcium, zinc, and zirconium being present assalts of acids selected from the group consisting of branched-chainaliphatic monocarboxylic acids having 6 to 14 carbon atoms,cycloaliphatic monocarboxylic acids having 6 to 10 carbon atoms, andmixtures thereof.
 14. The method of claim 13 wherein the loss-of-dryinhibitor contains 0.5 to 1.2 percent by weight of cobalt, 1.0 to 2.5percent by weight of calcium, and 2.5 to 4.0 percent by weight of zincor zirconium.
 15. The method of claim 13 wherein the loss-of-dryinhibitor comprises a solution of salts of acids selected from the groupconsisting of branched-chain aliphatic monocarboxylic acids having 8 to10 carbon atoms, naphthenic acid, and mixtures thereof.
 16. The methodof claim 13 wherein the loss-of-dry inhibitor contains 0.5 to 1.2percent by weight of cobalt as cobalt 2-ethylhexoate and cobaltisononanoate, 1.0 to 2.5 percent by weight of calcium as calciumnaphthenate, and 2.5 to 4.0 percent by weight of zinc as zinc2-ethylhexoate.
 17. The method of claim 13 wherein the loss-of-dryinhibitor comprises a solution of metal salts in a hydrocarbon solvent.18. The method of claim 13 wherein the loss-of-dry inhibitor comprises asolution of metal salts in mineral spirits.